CD4* helper T cells (hereinafter referred to as Th cells) involved in the onset of allergic diseases or autoimmune diseases are classified based on the type of the cytokines they produce into two types, namely, type I helper T cells (hereinafter referred to as Th1 cells) and type II helper T cells (hereinafter referred to as Th2 cells). Th1 cells produce IL-2, IFN-γ, TNF-β and the like, whereby inducing a cellular immunity. On the other hand, Th2 cells produce IL-4, IL-5, IL-6, IL-10, IL-13 and the like, whereby inducing a humoral immunity.
Th0 cells which are common precursors for Th1 cells and Th2 cells are differentiated into either Th1 cells or Th2 cells in response to an antigenic stimulation and then becomes mature. For example, a bacterium such as Bacillus tuberculosis and a virus such as an influenza virus are known to induce the differentiation to Th1 cells, while allergens such as a mite and a pollen are known to induce the differentiation to Th2 cells.
Recently, it has been reported that a polarized existence of Th1 cells and Th2 cells in a body is involved greatly in a prevention of infection and induction of allergic diseases or autoimmune diseases, and it is expected that inhibiting an excessive differentiation to Th2 cells serve to give a therapeutic effect against allergic diseases or autoimmune diseases induced by Th2 cells.
A compound having a backbone analogous to that of the present invention and having an immunosuppressive effect or an antiallergic effect is disclosed for example in WO94/27980, WO95/13067, WO96/15123, WO95/15318, WO96/40659, WO96/40143, WO96/38412, WO96/10012, WO97/24356, WO97/27181, WO97/24324, WO97/39999, WO97/44333, WO97/46524, WO98/04508, WO98/24766, WO98/24782, WO98/56785, FR2301250, U.S. Pat. No. 5,593,991, JP 47-7368 B, JP 51-91259 A, JP8-3163 A, JP 9-124571 A, JP 9-71564 A, JP9-124571 A, JP11-79993 A, Bioorganic & Medicinal Chemistry Letters, Vol. 5, No. 18, p2143-2146 (1995), J. Med. Chem., 1974, Vol. 17 and No. 11, 1177–1181.